/*
 * ProGuard -- shrinking, optimization, obfuscation, and preverification of Java bytecode.
 *
 * Copyright (c) 2002-2018 GuardSquare NV
 *
 * This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public
 * License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later
 * version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied
 * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along with this program; if not, write to the Free
 * Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */
package proguard.optimize.peephole;

import proguard.classfile.constant.Constant;
import proguard.classfile.editor.CodeAttributeEditor;
import proguard.classfile.instruction.Instruction;
import proguard.classfile.instruction.visitor.*;

/**
 * This InstructionVisitor replaces multiple instruction sequences at once.
 *
 * The replacement sequences are optional, defaulting to the empty sequence, to delete the matched pattern sequences.
 *
 * @see InstructionSequenceReplacer
 * @author Eric Lafortune
 */
public class InstructionSequencesReplacer extends MultiInstructionVisitor implements InstructionVisitor {
    private static final int PATTERN_INDEX = 0;
    private static final int REPLACEMENT_INDEX = 1;

    private static final Instruction[] EMPTY_INSTRUCTIONS = new Instruction[0];

    /**
     * Creates a new InstructionSequencesReplacer.
     * 
     * @param constants any constants referenced by the pattern instructions and replacement instructions.
     * @param instructionSequences the instruction sequences to be replaced, with subsequently the sequence pair index,
     *        the patten/replacement index (0 or 1), and the instruction index in the sequence.
     * @param branchTargetFinder a branch target finder that has been initialized to indicate branch targets in the
     *        visited code.
     * @param codeAttributeEditor a code editor that can be used for accumulating changes to the code.
     */
    public InstructionSequencesReplacer(Constant[] constants, Instruction[][][] instructionSequences,
        BranchTargetFinder branchTargetFinder, CodeAttributeEditor codeAttributeEditor) {
        this(constants, instructionSequences, branchTargetFinder, codeAttributeEditor, null);
    }

    /**
     * Creates a new InstructionSequenceReplacer.
     * 
     * @param constants any constants referenced by the pattern instructions and replacement instructions.
     * @param instructionSequences the instruction sequences to be replaced, with subsequently the sequence pair index,
     *        the patten/replacement index (0 or 1), and the instruction index in the sequence.
     * @param branchTargetFinder a branch target finder that has been initialized to indicate branch targets in the
     *        visited code.
     * @param codeAttributeEditor a code editor that can be used for accumulating changes to the code.
     * @param extraInstructionVisitor an optional extra visitor for all deleted load instructions.
     */
    public InstructionSequencesReplacer(Constant[] constants, Instruction[][][] instructionSequences,
        BranchTargetFinder branchTargetFinder, CodeAttributeEditor codeAttributeEditor,
        InstructionVisitor extraInstructionVisitor) {
        super(createInstructionSequenceReplacers(constants, instructionSequences, branchTargetFinder,
            codeAttributeEditor, extraInstructionVisitor));
    }

    /**
     * Creates an array of InstructionSequenceReplacer instances.
     * 
     * @param constants any constants referenced by the pattern instructions and replacement instructions.
     * @param instructionSequences the instruction sequences to be replaced, with subsequently the sequence pair index,
     *        the from/to index (0 or 1), and the instruction index in the sequence.
     * @param branchTargetFinder a branch target finder that has been initialized to indicate branch targets in the
     *        visited code.
     * @param codeAttributeEditor a code editor that can be used for accumulating changes to the code.
     * @param extraInstructionVisitor an optional extra visitor for all deleted load instructions.
     */
    private static InstructionVisitor[] createInstructionSequenceReplacers(Constant[] constants,
        Instruction[][][] instructionSequences, BranchTargetFinder branchTargetFinder,
        CodeAttributeEditor codeAttributeEditor, InstructionVisitor extraInstructionVisitor) {
        InstructionVisitor[] instructionSequenceReplacers = new InstructionVisitor[instructionSequences.length];

        for (int index = 0; index < instructionSequenceReplacers.length; index++) {
            Instruction[][] instructionSequencePair = instructionSequences[index];

            Instruction[] patternInstructions = instructionSequencePair[PATTERN_INDEX];

            // The replacement sequence is optional.
            Instruction[] replacementInstructions = instructionSequencePair.length > REPLACEMENT_INDEX
                ? instructionSequencePair[REPLACEMENT_INDEX] : EMPTY_INSTRUCTIONS;

            instructionSequenceReplacers[index] = new InstructionSequenceReplacer(constants, patternInstructions,
                constants, replacementInstructions, branchTargetFinder, codeAttributeEditor, extraInstructionVisitor);
        }

        return instructionSequenceReplacers;
    }
}
